Process for refining lubricating oil fractions



1966 J. D. BUSHNELL A 3,273,414

PROCESS FOR REFINING LUBRICATING OIL FRACTIONS Filed Sept. 27, 1962 74 a 75 72 /s3 #33 5' A 4- V I7 50 50 d3 60 /4O s s /k 5 e2 9 r l N a A 44 6 47A 2 Q 64 43B 45 48A ,6? 38 j l J' 36 f -BSA 47B 33/ JAMES o BUSHNELL HAROLD .N.WEINBERG entor By Cami/Q0 Patent Attorney United States Patent 3,278,414 PROE FQR REFINTNG LUBRTCATING OIL FRACTEONS James D. Bushnell, Eerkeley Heights, and Harold N. Weinberg, East Brunswick, NJ assignors to Esso Research and Engineering Company, a corporation of Delaware Filed Sept. 27, 1962, Ser. No. 226,505 4 Claims. ((11. 20834) The present invention relates to an improved process for producing lubricating oils and is concerned with the process steps of solvent deasphalting, solvent extraction, and solvent dewaxing. It relates particularly to the recovery of the solvents and to the maximum utlization of available heat energy in the process sequences. Specifically, it concerns improvements in combining the solvent recovery systems of the deasphalting and dewaxing plants.

More specifically, the invention relates to the use of a centrifugal compressor, driven by a gas turbine, for all deasphalting and dewaxing solvent compression services, and the utilization of the hot turbine gas exhaust as preheated combusion air for the solvent extraction treating unit furnaces.

There are two basic types of crude oil employed in lube manufacturing. They are paraffinic and naphthenic crudes. Naphthenic crudes generally do not require dewaxing. With paraflinic type crudes, however, varying degrees of dewaxing are required to obtain the desired pour point. Depending on the desired properties of the refined lubricating blending stocks, suitable feeds, ranging in boiling point from vacuum residual fractions to light lube distillate fractions are used.

To better understand applicants invention, a brief description of the various process steps and how they are related will be given:

Deasphalting The deasphalting process comprises contacting an asphalt-containing crude residuum with 2 to 12 volumes of liquid solvent, based on feed, at temperatures of 80 to 250 F. The residuum and the deasphalting solvent are countercurrently contacted. The overhead phase contains the deasphalted oil and most of the solvent. The rejected asphaltic phase is removed as bottoms and contains a minor portion of the solvent. The solvent present in the overhead and bottom fractions is removed by separately heating these fractions and flashing the solvent. The deasphalting step is normally the first in the sequence that is carried out. The feed to this step is normally the shortest of the residual fractions. Asphaltic feeds normally comprise the atmospheric residual fractions and vacuum residual fractions.

The deasphalting solvent normally comprises light hydrocarbons, such as ethane, propane, butane, and pentane and/ or mixtures thereof. The deasphalted oil may then be phenol treated, hydrofined, dewaxed, or sent directly to storage.

Solvent extraction A suitable feed, such as a lube distillate or deasphalted oil is contacted with a solvent which preferentially dissolves aromatic compounds. The removal of aromatics raises the viscosity index of the product and improves color and oxidation stability. Examples of suitable solvents are phenol, furfural, chlorex (2,2'-dichl oroethyl ether) and nitrobenzene. The solvent is countercurrent- 1y contacted with the feed in a treating tower, which separates into extract and raflinate phases. The raflinate contains the refined oil and some solvent, while the extract contains most of the solvent and the aromatic components. The solvent is recovered from the extract and rafiinate phases by distillation. The extract and raffinate ice phases are heated to about 600 F. in furnaces wherein most of the solvent vaporizes. Residual solvent is stripped out in the recovery towers by a stripping gas.

Dewaxing Waxy oil feed from any of the previously discussed process steps or other suitable sources is mixed continuously with a suitable dewaxing solvent. In accordance with this invention, the dewaxing solvent is propane or a mixture of propane, ethane, and butane. Since the dewaxing and deasphalting solvent recovery systems are integrated, the dewaxing solvent will be the same as the deasphalting solvent.

A small quantity of dewaxing aid may be added to the solvent feed solution. The feed is heated to a temperature sufiiciently high to dissolve any wax crystals present. It is then cooled to about F. and sent to a warm solution drum from which it is charged alternately to two batch chillers. In the chiller, the temperature is gradually dropped to about -30 F. by vaporizing liquid propane. Wax crystallizes out of solution as the temperature is reduced. The operation is arranged so that while one chiller is chilling, the other chiller is being emptied and filled for its next chilling operation. The filter feed drum receives the chilled batches from the chiller from which it continuously feeds one or more rotary filters. The temperature at which the solution is dewaxed is 0 to -50 F. The percentage of feed removed as slack wax is 2 to 50%, while the percentage of dewaxed oil obtained is 50 to 98%. The dewaxed oil passes through the filters and is collected. The filtered wax and the dewaxed oil are separately heated to recover solvent therefrom.

Process integration The two main integrating features of the integrated lube plant will be discussed below. They are the integrated solvent recovery system and the use of the hot turbine exhaust gases as preheated combustion gas for the extract and raflinate furnaces.

The solvent recovery facilities for dewaxing and deasphalting units have been combined. The same compressor, condenser, storage drum, knockout drum, and associated piping are used for the dewaxing and deasphalting plant propane circulation systems. Solvent recovery is accomplished in two stages; one flashing at high pressure and the other flashing at low pressure. The bulk of the solvent is recovered from the slack wax solution, the dewaxed oil solution, and the deasphalted oil solution at a temperature of about to 300 F. and a pressure of about 200 to 300 p.s.i.g.; whereas, the solvent from the asphalt solution is recovered at a temperature of about 400 to 600 F. and a pressure of about 200 to 300 p.s.i.g. The higher temperature for recovery of the solvent from the asphalt fraction is desirable to avoid carryover due to high liquid viscosities of the asphalt solution. Low pressure flashing is carried out subsequent to the high pressure flash to remove the last traces of propane from the streams and is otherwise similar to the high pressure flash stage. The propane solvent from the high pressure flash drums is condensed and sent to storage. The propane vapor from the chillers and the low pressure flash drums is compressed, condensed, and sent to propane storage.

A single, centrifugal compressor driven by a gas turbine is used for all propane compressor services. The hot turbine exhaust gas is used as preheated combustion air for the extraction plant solvent recovery furnaces.

The integration of various process steps has resulted in a substantial over-all savings in investment and operating costs. These savings have reulted from the integration of the solvent recovery systems and use of the high temperature gas turbine exhaust gases as preheated combustion air for the phenol plant raflinate and extract furnaces.

This invention may be more readily understood by referring to the accompanying drawings which illustrate specific embodiments of the invention. The drawings have been simplified by omitting various pumps, compressors, motors, heat exchangers, which are conventional and which do not form a part of the present invention. the drawing describes in detail the deasphalting and dewaxing process steps as well as the combined propane solvent recovery system.

The invention will be described in relation to a feed undergoing deasphalting, phenol treating, and dewaxing. A residuum feed, boiling in the range of about 950 to 1300 F. is fed through line 1 to the top of deasphalting tower 2 and countercurrently contacted with an ascending stream of liquid propane introduced through line 3 at a ratio of propane solvent to feed of about 8: 1. The contacting step is carried out at a temperature of about 160 F. and at about 500 p.s.i.g. In treating tower 2 the residuum is separated into an asphaltic solution and a deasphalted oil solution by the precipitating action of the propane on the asphaltic materials. The deasphalted oil/ propane solution is taken overhead through line 4 and heated from about 170 to 360 F. by heat exchange means, not shown. The heated solution is fed through line 4 to the bottom of high pressure flash drum 6 and flashed at an elevated temperature and pressure. The flashed propane vapor from the high pressure flash drum is removed by line 7 and joins propane solvent in line 8. Line 8 picks up overhead flashed propane from the other high pressure flash drums and sends it to main propane condenser 9.

The precipitated asphaltic propane solution is withdrawn from deasphalting tower 2 through line 10 and is heated from about 160 F. to about 540 F. and then continues through line 10 to section 11 of the high pressure flash drum wherein it is flashed at an elevated temperature and pressure.

The flashed propane vapors are taken overhead by line 12 and join line 8 and are conveyed to main propane condenser 9 via line 74. The bottoms containing the asphaltic constituents and a small amount of propane are sent to the low pressure flash drum 13 through line 14 to recover the small amount of propane remaining. The propane recovered by flashing in the low pressure flash drum is withdrawn by line 15, collected in line 16 and sent to condenser 9 via knockout drum 17, and compressor 49.

The deasphalted oil is removed from high pressure flash drum section 6 by line 18 and sent to low pressure flash drum 19, where the small amount of propane remaining in the oil is flashed. The removed propane is taken overhead through line 20 and joins line 16 going to knockout drum 17, compressor 49 and then condenser 9. The asphaltic materials are removed from the bottom of flash drum 13 by line 21 and taken to storage or for further processing.

The deasphalted oil withdrawn from the low pressure flash drum 19 is fed into the bottom of the phenol treating tower 23 through line 22 and is countercurrently contacted with liquid phenol fed into the top of tower 23 through line 24. The feed is first heated to a temperature of about 200 F. A raflinate phase is removed overhead through line 25. The extract phase is removed from the bottom of phenol treating tower 23 through line 26. The extract phase contains most of the phenol solvent and extracted aromatic constituents.

The overhead raflinate stream contains a small amount of phenol solvent and most of the nonaromatic components. The reffinate stream in line 25 is fed to furnace F-2 through line 25 where it is heated to about 650 to 700 F. The phenol is partially vaporized and sent to raffinate phenol recovery tower 27 through line 28, where the phenol solvent is separated from the raflinate. Phenol solvent recovery is maximized by stripping with gas, in a conventional manner. The hot phenol vapors leave towel 27 via line 29 at about 425 to 450 F. and about 40 to 60 p.s.i.g. They are subsequently combined with the phenol solvent vapors from tower 30 in line 31. Line 31 leads to the phenol vapor condensing system. Condensed phenol is accumulated and stored in drum 32. The raflinate, free of phenol solvent, is removed from phenol solvent recovery tower 27 by line 33 and fed to the dewaxing plant. The phenol extract fraction from phenol treating tower 23 is removed from the bottom of the tower through line 26 and fed through line 26 to phenol extract recovery tower furnace F-l where it is heated to about 575 to 625 F., partially vaporizing the phenol solvent. The partially vaporized phenol and extract are fed through line 33B to extract recovery tower 30. Hot phenol vapors are taken overhead through line 34 where they are combined with the vapors from ratfinate recovery tower 27 in line 31. Phenol solvent recovery is increased by stripping with a gas. The bottoms product is discharged, at a temperature of about 500 to 600 F., from tower 30 through line 35.

The phenol treated oil from phenol raflinate recovery tower 27 is introduced into the the dewaxing plant through line 33 into propane mixer 36 wherein liquid propane is mixed with the feed at a pressure of about 350 p.s.i.g. The mixture of propane and feed is then heated to a temperature sufliciently high to dissolve any wax crystals that may be present in the feed. The feed is then cooled to about F. and charged to the warm solution drum 38, from which it is fed alternately through lines 41 and 42A and 42B to each of two batch chillers 39B and 39A.

To simplify the description of the dewaxing operation, only one chiller and one filter Will be described in detail. A batch of waxy feed/propane solution is chilled by vaporizing some of the propane which is removed overhead by line 40. Druing the chilling, the wax present in the feed crystallizes. The operation is arranged so that while one chiller is chilling, the other chiller is being emptied and then filled for its chilling operation.

The chilled solution then goes through lines 43A and 43B to filter feed drum 45 via line 44. From the feed drum 45 the wax crystals, propane solvent and oil are continuously fed through lines 46, 47A, and 478 to wax filters 48A and 48B, where the precipitated wax is separated from the oil/wax/solvent mixture. Propane vapors from the warm solution drum 38, chillers 39A and 39B, and filter feed drum 45 are throttled to about 3 p.s.i.g. and sent through line 40 to knockout drum 17 and compressor 49.

The chilled solution, fed through line 47A and 47B is separated into wax and dewaxed oil by filters 48A and 48B. The dewaxed oil passes through the filter cloth into a rundown drum, not shown, and then to the propane recovery system. The wax deposited on the filter cloth is Washed by liquid propane. The wax cake is removed from the filter by propane blowback gas supplied by line 50. The dewaxed oil/propane solution is removed from the filter by line 51 and is heated to about 340 F. by heat exchange means, not shown.

The dewaxed oil/ propane solution then enters high pressure flash drum 52 through line 51 where it is flashed at an elevated temperature and pressure. Most of the propane in the dewaxed oil solution is removed in the high pressure flash drum through line 533 which joins line 8 going to propane condenser 9. The dewaxed oil is removed from the bottom of drum 52 by line 53A and sent to low pressure flash drum 54, wherein the small amount of propane remaining is flashed at about 5 p.s.i.g. The propane vapor is removed overhead by line 55 and joins in line 16 the propane vapor en route to knockout drum 17 and propane compressor 49. The dewaxed oil, free of propane, is removed from drum 54 by line 56 and sent to lubricating oil stock storage. This stream constitutes the deasphalted, phenol treated, dewaxed oil product.

The slack wax slurry is removed from the filter 4813 by line 57, and heated to about 320 F. The slurry is fed thorugh line 57 to high pressure flash drum 58 wherein the propane is flashed at an elevated temperature and pressure. Most of the propane is removed overhead through line 61. The slack wax is withdrawn from flash drum 58 by line 59 and is sent to knockout drum 17, to remove any small amount of propane remaining. The slack wax, free of propane, is removed from knockout drum 17 as bottoms through line 60 and can be further processed to recover wax, cracked to make lighter products or used as fuel. The propane vapor from the high pressure flash 58 is removed through line 61 and joins line 8 and is sent to propane condenser 9. The propane vapors in line 8 are condensed in condenser 9 and sent to propane accumulator drum 62.

In the propane recovery system, the same compressor 49, condenser 9, storage drum 62, knockout drum 17, and associated piping, are used for both the deasphalting step and the dewaxing step. A single centrifugal compressor 49 driven by a gas turbine 63 is used for all propane compression services. The propane recovery system takes solvent vapor streams from the low pressure flash drums 19, 13 and 54, chillers 39A and 39B, filters 48A and 48B, warm solution drum 38 and filter feed drum 45 and sends them to propane knockout drum 17. From there, they go to propane compressor 49 where the pressure is raised from about 3 to 5 p.s.i.g. to about 200 to 250 p.s.i.g. The compressed propane is condensed in condenser 9 and sent to propane accumulator drum 62. Propane vapors from the high pressure flash drums 58, 52, 11 and 6, at about 200 to 250 p.s.i.g. are introduced by line 8 into condenser 9, condensed, then fed into propane accumulator drum 62 through line 64-. Liquid propane is fed through line 3 to deasphalting tower 2 where the deasphalted step is carried out and through line 67 to dewaxing propane mixer 36, respectively, where the dewaxing step is carried out.

A gas turbine 63 drives the single centrifugal propane compressor 49 through conventional mechanical connection 72. Combustion air at ambient temperature, for the turbine, is introduced into turbine 63 through line 68 wherein it is mixed with fuel and the fuel ignited, driving the turbine wihch provides the energy to drive compressor 49. Exhaust gases at a temperature of about 900 to 1000 F. and containing about 16 to 18% 0 are exhausted through line 69. Line 69 divides into lines 70 and 71, providing preheated combustion air to extract furnace F-1 and raffinate furnace F-2, respectively. The use of the hot turbine exhaust gases results in about a 20% fuel savings since the heat to raise the combustion air from ambient temperature to the 900 to 1000 F. is not required.

The invention is understood to include other operating temperatures and pressures than those described, as well as the use of other solvents. Obvious variations in the treating steps and sequence of treating steps which occur to those skilled in the art are also contemplated to be Within the scope of this invention.

While preferred embodiments of the invention have been illustrated, it is to be understood that the invention is not limited in its scope to the embodiments shown, but rather by the scope of the appended claims.

What is claimed is:

1. In combination a deasphalting plant, a dewaxing plant and a solvent extraction plant, in which the same solvent is used in deasphalting and dewaxing and a second solvent is used in solvent extraction, and process streams from the deasphalting and dewaxing plants are treated to recover said solvent in a compressor containing solvent recovery system said second solvent from the extraction plant is recovered from extract and raffinate phase process streams by heating, in a furnace, the improvement which comprises passing all of said solvent obtained from the deasphalting and dewaxing step to a single combined deasphaltin g and dewaxing solvent recovery system wherein all compressor services are provided by the same compressor wherein the said compressor is driven by a gas turbine drive powered by combustion of fuel to provide hot oxygen-containing exhaust gases and wherein the hot exhaust gases from said gas turbine are utilized as preheated combustion air for the second solvent extraction plant extract and raffinate furnaces.

2. The process of claim 1 wherein said solvent is propane and said second solvent is selective to aromatics.

3. The process of claim 2 wherein said second solvent is phenol.

4-. The process of claim 1 wherein the turbine exhaust gases are available at a temperature of 700 to 1200 F. and contain about 15 to 20% oxygen.

References Cited by the Examiner UNITED STATES PATENTS 1,989,355 1/1935 Gard 208-34 2,218,517 10/1949 Bray 208-34 3,002,347 10/1961 Sprague -39.12

OTHER REFERENCES Perry: Chemical Engineers Handbook, Third Ed., (1950), pp. 1713, McGraw-Hill Book Co., Inc., New York.

Nelson: Petroleum Refinery Engineering, Fourth Ed. (1958), pp. 238 to 241, 347 to 352 and 362 to 364, Mc- Graw-Hill Book Co., Inc., New York.

DELBERT E. GANTZ, Primary Examiner.

ALPHONSO D. SULLIVAN, Examiner.

H. LEVINE, Assistant Examiner. 

1. IN COBINATION A DEASPHALTING PLANT, A DEWAXING PLANT AND A SOLVENT EXTRACTION PLANT, IN WHICH THE SAME SOLVENT IS USED IN DEASPHALTING AND DEWAXING AND A SECOND SOLVENT IS USED IN SOLVENT EXTRACTION, AND PROCESS STREAMS FROM THE DEASPHALTING AND DEWAXING PLANTS ARE TREATED TO RECOVER SAID SOLVENT IN A COMPRESSOR CONTAINING SOLVENT RECOVERY SYSTEM SAID SECOND SOLVENT FROM THE EXTRACTION PLANT IS RECOVERED FROM EXTRACT AND RAFFINATE PHASE PROCESS STREAMS BY HEATING, IN A FURNACE, THE IMPROVEMENT WHICH COMPRISES PASSING ALL OF SAID SOLVENT OBTAINED FROM THE DEASPHALTING AND DEWAXING STEP TO A SINGLE COMBINED DEASPHALTING AND DEWAXING SOLVENT RECOVERY SYSTEM WHEREIN ALL COMPRESSOR SERVICES ARE PROVIDED BY THE SAME COMPRESSOR WHEREIN THE SAID COMPRESSOR IS DRIVEN BY A GAS TURBINE DRIVE POWEDERED BY COMBUSTION OF FUEL TO PROVIDE HOT OXYGEN-CONTAINING EXHAUST GASES AND WHEREIN THE HOT EXHAUST GASES FROM SAID GAS TURBINE ARE UTILIZED AS PREHEATED COMBUSTION AIR FOR THE SECOND SOLVENT EXTRACTION PLANT EXTRACT AND RAFFINATE FURNACES. 